Effects of Grapefruit on Energy Balance, Weight Loss, Body Composition, and Cardiometabolic Risk in Obese Adults

Yet, much discussion continues regarding the optimal form of a preload. The purpose of the present study was to compare effects of a solid (grapefruit), liquid (grapefruit juice) and water preload consumed prior to breakfast, lunch and dinner in the context of caloric restriction.

Eighty-five obese adults (BMI 30-39.9) were randomly assigned to (127 g) grapefruit (GF), grapefruit juice (GFJ) or water preload for 12 weeks after completing a 2-week caloric restriction phase. Preloads were matched for weight, calories, water content, and energy density. Weekly measures included blood pressure, weight, anthropometry and 24-hour dietary intakes. Resting energy expenditure, body composition, physical performance and cardiometabolic risk biomarkers were assessed.

The total amount (grams) of food consumed did not change over time. Yet, after preloads were combined with caloric restriction, average dietary energy density and total energy intakes decreased by 20-29% from baseline values. Subjects experienced 7.1% weight loss overall, with significant decreases in percentage body, trunk, android and gynoid fat, as well as waist circumferences (-4.5 cm). However, differences were not statistically significant among groups. Nevertheless, the amount and direction of change in serum HDL-cholesterol levels in GF (+6.2%) and GFJ (+8.2%) preload groups was significantly greater than water preload group (-3.7%).

From the results, this data indicate that incorporating consumption of a low energy dense dietary preload in a caloric restricted diet is a highly effective weight loss strategy. But, the form of the preload did not have differential effects on energy balance, weight loss or body composition. It is notable that subjects in GF and GFJ preload groups experienced significantly greater benefits in lipid profiles.

The findings complement the accumulating body of evidence demonstrating that clinically significant weight loss can be achieved when consuming a low energy dense preload before meals. Notably, researchers demonstrated that this type of dietary intervention can occur without decreasing the total amount of food consumed, and thus, without inducing the hunger and dissatisfaction often associated with restrictive diets. Compared to pharmacological trials in free-living obese adults where attrition rates range from 30-40%, a high completion rate (80%) was achieved, further indication that subjects found the preload strategy satisfying, and they may have gained intrinsic value from interactions with study RDs.

Further, researchers extended the evidence by showing that the preload strategy can reduce dietary energy density and total energy intakes in obese adults in free-living conditions regardless of the form of the preload.

Obese individuals such as these might be more inclined to utilize the concept of "volumetrics" if encouraged to choose the form of their low energy dense preload based on individual preference. The data supports such choice in the context of a dietary weight loss intervention and suggests that such interventions have a fundamentally physiological basis.

Importantly, the bioactive components of some preloads, like GF and GFJ, may confer additional cardiometabolic benefits as evidenced by the very significant increases in serum HDL-cholesterol concentrations in the present trial. Clearly, additional clinical research is needed to investigate the mechanisms by which fruit, juice and water influence energy intake regulation and lipid metabolism.  

Nutr Metab. 2011;8